Many devices and systems include a number of different types of sensors that perform various monitoring and/or control functions. Advancement in micromachining and other microfabrication processes have enabled the manufacture of a wide variety of microelectromechanical system (MEMS) devices.
A MEMS device is one type of electronic device that has a movable mass. A particular type of sensor that includes a MEMS device is an accelerometer that uses a movable mass to detect acceleration or other stimulus along a sensing direction. In a typical accelerometer, the movable mass forms part of a differential capacitor pair. The motion of the movable mass is detected by a sensing circuit coupled to the differential capacitor pair, and the acceleration of the MEMS device can thereby be calculated.
The movable mass in a typical MEMS device is suspended in proximity to a substrate with one or more suspension structures. The suspension structures can be folded to have a number of elbows to provide a space efficient design and to reduce the effects of package stresses on the MEMS device. However, portions of the suspension structures can disadvantageously touch and stick together under certain loading conditions. This situation is known as “stiction” and can cause malfunction of the MEMS device.
Accordingly, it is desirable to provide a MEMS device with a reduced occurrence of stiction. In addition, it is desirable to provide a method of reducing stiction in a MEMS device.